Attrition-mill



UNITED STATES PATENT OFFICE.

THOMAS L. STURTEVANT, 0F EEAMINGHAM, MAsSAeHUsETrs.

ATTRlTioN-MILL.

SPECIFICATION forming part of Letters Patent No. 255,550, dated March28, 1882.

` Application filed January 1G, 1882. (No model.)

To all whom 'it muy concern f Be it known that I, THoMAs LEGGETTSTURTEVANT, a citizen of the United States, residing at Framingham, inthe county of Middlesex and State of Massachusetts, have inventedcertain new and usefulY Improvements in Attrtion-Mills; and I do herebydeclare the following to be a full, clear, and exact description of theinvention, such as will enable others skilled in the art to which itappertains to make and use the same, reference being had to the4accompanying drawing, and to letters 'or iigures of reference markedthere, on, which forms a part ofthis specification.

The object of this invention is to grind to powder phosphate,grains,ores, or other sub1 stances; and it consists, first, in a methodof grinding such substances, which consists in compelling one portion ofthe mass of material to remain stationary, or practically stationary,while another portion revolves, whereby the entire massitselfprovidesnot only its own grinding-surfaces, which are renewedcontinually, as the tlour is removed, but also the material tombeground; second, in a mill for carrying out such method, consisting of acircular recessed wheel or head supported upon a suitable rotary shaft,and combined with a hopper or case for containing the material to beground and presenting it to theopen face of such head, all substantiallyas hereinafter explained.

The drawing accompanying this speciica tion represents a centralvertical longitudinal section of a machine embodying my invention.

Reference being had to the above-named drawing, A will be seen torepresent a circular head or disk, open or recessed at one` end, and atthe other secured to one end of a horizontal shaft, B, mounted in astandard or standards, C G, iusuch manner as to rotate freely in thelatter, said shaft being provided with a fast and loose pulley.

Upon the front edge of the chambered head A may be formed an annular lipor ledge, b, the diameter of the mouth of which is less than that of thechamber c of the head, in order to prevent liability'of the centrifugalforce expelling the contents of such chamber; or this chamber may befrustoconieal in form, with its smallest diameter ,at the mouth; or itmay be of the form of a bowl with a contracted mouth,for thesamepurpose. I do not con-v sider these contractions of the chamber bab-v solutely essential, but prefer to employ some one ot' them.

D in the accompanying drawing represents a box or case open at top, or ahopper, as it is usually called, thelower and closed part, d, of thishopper communicating with the chamber c ot' the head A by an opening, e,preferably of the size of the mouth of the said chamber. l

A suction or blastfan may be employed to extract or expel the liour fromthe hopper.l This may bc placed either at the top or bottom, or at anydesirable point; and the open# ing into said hopper is preferablycovered by a reticulated screen to prevent the escape of ungroundparticles.

In the use ot' this mill a considerable quantity of the material to beground, which is supposed to bein a granular state, or in lumps orblocks, is supplied to thehopper or case I), and the greater part ofsuch hopper, as well as the entire chamber c, filled with such ma terialand the head Aput in rapid rotation.

I have found by extended practical tests that the centrifugal forcegenerated by the rotation of the head A tends to maintain the-unground-material in the chamber c, and the faces being renewed by thesupply constantly furnished to the hopper.

I have shown the recessed head A as arranged to rotate upon a horizontalaxis, with the hopper supplying it in front; but the head may bedisposed to rotate in a horizontal plane upon a vertical Shaft and befed from the top.

A modified constructionof the above mill would be to employ two rotaryrecessed wheels arranged upon opposite sides of the hopper and rotatingin opposite directions, the hopper having an opening communicating witheach.

I propose under some circumstances applying flanges or ribs to the innerperiphery of the head A to prevent possibility of movement of the massof material upon such periphery.

I am aware that in attrition-mills an apparatus has been constructedwith two wheels revolving in opposite directions. The material is fedthrough a hopper 011 each side and falls by gravity into revolvingchannels formed :in said wheels, and by means of radial partitionsseparating the channels from each other has the velocity of the wheelsimparted to it. Owing to this centrifugal force it will tend to advancethrough said channels and out through the circumferential openings ofsaid channels. When the material has reached this point it meetsasimilar stream striving to escape through opposite channels in a similarway, and these two streams are pressed and ground against each other bymeans of the centrifugal force acquired from the revolution ofthewheels. My method, although having the same general broad principle ofgrinding by means of utilizing the material for the grinding-surfaces,has also the principle of having one mass to remain stationary whileanother mass revolves in a circular head about it. The material, be itof granular or other substance, does the grinding. This broadprinciple-has been shown to be not new in the art; but my method, asherein before described, certainly is an improvement on the process setforth as above. This process is an unrelia` ble one,depending entirelyupon the pressure with which the particles are brought together. Thispressure, as stated, is derived lfrom the centrifugal force imparted bythe wheels. When less velocity is used the force isjust so much less,and the pressure of the grain consequently less, and thus the grindingwould often be unsatisfactory. There is also danger of the channelsbecoming clogged by the grain itself'. One lnass comingoneway andanother mass striving to reach the same place would tend to mix up andclog the openings. There are no such dangers existingin my apparatus. Icause one mass to remain stationary and constantly supply the other masswhich rotates about it in a recessed chamber, the grinding being done bythe impact of the rotary vsolid mass against the stationary solid mass.

There are no channels to become clogged, and the pressure of the twomasses of material upon each otheris always the same, and therefore thematerial will always be ground satis,- factorily. This principle ormethod of mine will Work better, and the apparatus therefore is simplerand consequently less expensive t-han has hitherto been used in suchmills.

I claiml. The method, substantially as herein described, ofgrindingvarious substances, which consists in compelling one portion of the massof material to be ground to remain in a passive state, whileanother-portion revolves in a compact or coherent body upon it, theintermediate shifting portion being ground by friction or attritionbetween its own particles, the entire massitself thus providing not onlythe grinding-surface, but the material to be ground, and the supplybeing continuously furnished to the hopper.

2. The mill herein described, consisting of the rotary chambered head,in combination with thehopper arranged to communicate with and supplythe chamber of such head, substantially as set forth.

In testimony whereofI affix my signature in presence of two witnesses.

, THOMAS LEGGETT STURTEVANT.

Witnesses:

F. CURTIS, H. E. LODGE.

